Means fob purifying polluted liquids



Feb. 22, 1944. c H syn 30 Re. 22,444

MEANS FOR PURIFYING POLLUTED LIQUIDS Original Filed April 29, 1955 ATTORNEY Reissuecl Feb. 22, 1944 MEANS FOR PURIFYING POLLUTED LIQUIDS Charles H. Shook, Dayton, Ohio, assignor to Infilco Incorporated, a corporation of Delaware Original No. 2,097,779, dated November 2, 1937,

Serial No. 18,925, April 29, 1935.

Application for reissue February 23, 1939, Serial No. 258,111

Claims.

This invention relates to a new and useful process of, and means for, purifying polluted liquids.

Polluted liquids such as sewage ar composed, among other things, of nitrogen bearing compounds which must be oxidized to insure good purification.

There are three common methods of biologically oxidizing the nitrogen compounds in poiluted liquids: the oldest, and now practically,

abandoned, system of intermittent sand filtration; the trickling filter; and the activated sludge method. Sand filters are very large and filtration rates are slow. Trickling filters as ordinarily employed are smaller than sand filters and allow much higher rates of sewage application. The activated sludge system is temperamental in its behavior, and expensive in construction and operatlon.

While this invention relates to the recirculation or polluted liquids through a trickling filter to increase its emclency, whether the filter be back or a chemical plant or any other type of plant, or be the sole unit or a system, it is particularly concerned with the recirculation 01 such liquids through a trickling filter that is back 0! a chemical plant.

It would seem to be a logical conclusion that if an impure liquid receives purification by passing once down through a depth oi. trickling filter, a second passage oi that liquid through the filter would be bound to improve it to some degree.

While a given quantity of a polluted liquid passing twice through a continuously operating filter will not be contained therein twice as long as the same quantity of liquid passing only once through such a filter, the liquid in the first case will be in contact with the filter media somewhat longer than the liquid in the second case, resulting in more efilcient'purificatiun.

The chief value, however, of'recirculation lies in the inoculation or activation obtained. The biologic growths or cultures, which we see in the form of slime or jelly at different levels in the ordinary trickling filter, vary tremendously. It a liquid is discharged onto a customary trickling filter. the top layer acts to strain out the suspended material, the next layer to inoculate the liquid with oxidizing organisms, and the rest of the filter to carry out the oxidation process. If liquid which has once passed through the filter, and which contains oxidizing organisms, is put back in the top of the filter, it follows that much more of the filter can be utilised to carry out the oxidizing process. The biologic growth, or bacterial slime, which continually sloughs irom the filter, may prove of exceptional value in activating the nlter and should be returned separately or in coniunction with the liquid if desired.

Among other things, the removal or suspended and colloidal organic material prior to filtration, decreases the load upon the filter. By removin this material first, there is actually less work for the filter to do, and consequently it can be smaller per gallon or liquid treated. Also, if these organic solids are prevented irom being deposited in the top layer or the filter, less danger irom clogging and consequently better air circulation through the filter W111 result.

Organic material in solution is immediately available ior oxidation by the filter, whereas solid material can digest on the outer surface only.

.It is well known that a cake of ice disintegrates much faster when broken into small pieces than if it were lelt in a large cake. So it is with solids on a filter. The smaller the particles, the more rapid the digestion, Consequently, if only the soluble solids are discharged to the filter, its efliciency should be increased.

To insure complete efficiency in a system under which the trickling filter is placed back of a chemical plant, the pH value of the discharge to the filter must be maintained nearly constant. It is found that bacteria are seriously ailected by changes in pH, and that the limits are relatively narrow. It is possible to accustom them to a pH value that is higher or lower than their normal point, but this must be done gradually. The fiuctuations in pH that are found in normal sewage, therefore, are not conducive to the best filter action.

If chemical treatment, therefore, is applied to sewage ahead of trickling filter dosage, or any biologic treatment, the pH value 01 the discharge to the filter may be maintained nearly constant. Further, it can be maintained at a value that is particularly conducive to the purifying action of the organisms present. This value, it has been found, is within the alkaline range, where the nltrifying bacteria are more eflective. The nitrifying organisms are the ones which oxidize the nitrogen bearing compounds of such polluted liquids as sewage, and, consequently, anything done to promote their activity, will be beneficial.

It is therefore one o! the principal objects of this invention to first treat the liquid to be purified with chemicals, not only to settle out finely divided and collo dal material but to maintain that liquid at a relatively uniform pH after which the material remaining in the treated liquid is oxidized by biologic action. This oxidation may be eflected by passing the treated liquid through a trickling filter, or through granular material, such as sand, or by aeration and activation.

As the human body can function more efliciently at certain uniform temperatures, so can the nitrifying bacteria be made more efiective in oxidizing the nitrogen bearing compounds of polluted liquids, such as sewage, at a uniform pH. Therefore, it is a particular object of this invention to maintain the pH constant, within the alkaline range during the chemical treatment of the liquid ahead of the trickling filter dosage or other biologic action. This constancy, or uniformity of the pH value, is maintained within the alkaline range in my system by the addition of lime or marl to the liquid under treatment.

After the chemical treatment of the polluted liquid at a constant pH is completed, the liquid containin in solution such solids as sugar, that cannot be precipitated out, is conducted to a trickling filter.

It is therefore another important object of this invention to recirculate this treated liquid, or any other liquid that passes through the filter, ,to uniformly distribute the biologic growth or culture therein, as well as to inoculate and activate the incoming unfiltered liquid.

Through recirculation active oxidizing organisms are sent back to inoculate the incoming liquid. This inoculation starts purification. However, this preinoculation enables the top part of the filter to function more effectively than it would without such inoculation. By placing this bacterial slime, or jelly, more uniformly throughout the filter oxidation of the filtered liquid is aided, clogging is reduced, and increased loading of the filter permitted.

It is anoth object of the invention to return the clear lieu bacterial is, or botl'i, or any part of eithei a liquid. the purpose of this i means may be provided for taking this l :Zrcm the humus tank, or the bottom of the tacle intermediate oi not able, however. to crovidc r return liquid when desired, a small deposited in the humus tank.

In large installations it would he more economical to connect the zetui l to the. bottom of the filter, because than it not be necessary to build such a. large humus tank. at the some time, a sin Trpipe could be composted between the bottom of ti humus tan ml the return line to draw from s *1 tank sr as desired. It the return. line 1c ccnncc n to the humus alone, the latter would have to be of large size, otherwise some of the solids that ordinarily settle to the bottom oi the tank would pass out into the stream into which the filtered liquids are ultimately discharged.

It another important object of this invention to provide for the return of the filtered liquid to the dosage tank through the same pipe which discharges the liquid from this tank into the filter.

Other important and incidental objects will be brought out in the following specification and particularly set forth in the subjoincd claims.

In the drawing the figure is a schematic view, partly in section, of one form of apparatus for practicing my filtration process.

Referring to the accompanying drawing for a tank detailed description of my process of filtering polluted liquids as practiced by the use of the apparatus therein disclosed, the numeral I designates a trickling filter which consists in this instance of a tank 2 containing filtering material that obviously may be of various substances but in this instance comprising broken rocks 3 that present suitable surfaces for the adherence of growing bacterial slime or jelly.

In the present instance the liquid to be filtered is distributed upon the top of the filter bed 3 by a rotatable spray head 4 carried by a short vertical riser' 5. This riser is fitted in a T applied to one end of a horizontal inlet tube I which is connected to the lower end of a dosage tank 8, although it may lead directly from any receptacle containing a polluted liquid to be filtered.

The dosage tank 8 is in communication with a sedimentation tank 9 through a horizontal tube ill. This tube leads from a. skimming gutter ll in the upper portion of the tank 9 to the top oi the dosage tank, where it is connected by a bend I! to a tube i3 that projects downwardly to a point near the bottom of the tank to deliver thereto liquid that is skimmed from the tank 9. Sediment from the latter tank is drained off through the pipe M.

The polluted liquid, after being chemically treated in a box IE to settle out much of the solid matter it holds in suspension, flows from the top of that box through a horizontal pipe I6 and connected vertical tube 11 to the bottom of the sedimentation tank. 9.

As will now be observed, 1 have illustrated in the drawing a trickling filter which is placed behind a chemical plant. To insure complete eificiency in such a system, the pH value of the discharge to the filter must be maintained at a constant pH value for the reasons heretofore given. This result is achieved in the present an aratus by the treatment at the liquid in the 5 with such chemicals ferric chloride lime and marl.

..ved or the solids which settle out oi it in X E5, in: liquid passes from the top oi. that bottom oi the tank 9, where a further takes place. in the r: mriining however. there is present 1n solution such so.- u e compounds as sugar vulzlcn cannot be by chemical treatment and deposition. tlon rises to the skimming gutter ii in 9, from which it flows o the bottom of dosage tank 8 for a conlml ed delivery through. the tube l and rotating spray head 4 to the top of P c trickling filter i j '5 heretol'ore stated, it is eminently desirable t e filtc ed liquid bute more uniformly tlll'Oll'gllOlli; the tank inc-logic growth which is or :oinerily found more prevalent in the lower n t oi the filter. The returned liquid not only carries this bacterial slime or culture to those portions of the filter where it is not present, but inouuls es the incoming liquid with these active or 1 organisms.

' Such inoculation starts purification.

The apparatus for recirculating the filtered liquid will now be described. Connected to the sloping bottom of the tank I by a bend it is one end of a horizontal tube 19, to the other end of which there is secured a short vertical pipe 20 which projects into a receptacle 2!. Below this receptacle is a humus tank 22 into which the filtered liquid delivered to the tank 2! is adapted to flow from the latter through a horizontal pipe 23 and connected vertical tube 24. This tube dis- The tube 1 which conducts the treated liquid 5 from the dosage tank to the filter, also BQIVBSi in the present apparatus to return the filtered liquid to that tank for recirculation through the filter. In order that the tube 1 may perform this dual function, I provide the following means for periodically reversing the fiow of liquid through Connected to the lower end of the T 6, through a short tube 26 and bend 21, is a horizontal pipe 28 which communicates at its other end, through a check valve 29 and meter 10, with a centrifugal return pump 8|. Through a vertical tube 32 projecting from this pump into the bottom portion of the receptacle 2i, filtered liquid is drawn from the latter by the pump and forced through the valve 2!, and pipes 28 and I, into the dosage tank when the pump is operated by the following means.

Secured'to the pump shaft 33 is a pulley 34 which receives a belt 35 that is driven by the armature shaft 36 of an electric motor 31. This motor is started and stopped by a conventional electric switch 38 from which a connecting wire 39 leads to the motor. Another wire 40 connected to the motor, and a wire ll connected to b the switch, include both in a circuit supplied with current by a source not shown.

When the liquid descends to the bottom of the, dosage tank 8, it carries down with it a float l! to which there is attached an upwardly'projectby the descending fioat, the switch 38 will close the electric circuit to the motor ll, which in turn will operate the pump 3| to return the filtered liquid from the receptacle 2| together with some of the solids from the humus tank 22, to the dosage tank 8, through the same pipe I that carried the liquid to the filter. These solids are drawn from the humus tank through a pipe 12' connected between the humus tank and the tube 32. During this return flow of the liquid, the

spray head still continues to revolve, because a part-of this liquid will be forced into the riser i for distribution upon the top of the filter bed. A part. of the filtered liquid, however, is returned to the dosage tank 8 to inoculate the incoming unfiltered liquid.

When the fioat I2 is carried by the incoming liquid to a pre-determined level, the collar 44 will engage the switch arm 46 to open the switch 38 and thereby stop the motor. The filtered liq uid, together with the fresh liquid which it has no inoculated with the active oxidizing organisms it has carried into the dosage tank from the filter and the humus tank, will now flow back to the spray head through the pipe I, for distribution upon the top of the filter bed 3. The recircula- 05 tion of this filtered liquid through the filter more uniformly distributes therein, and more particularly deposits in its top portion. the bacterial slime or jelly-which it has gathered from the bottom part of the filter in its previous descent 7o therethrough. One part of the filter will therefore more nearly approach the emciency of any other part in the process of oxidation.

This recirculation of the filtered liquid as many stance through the single pipe I by means of the electrically operated pump 3|, whose operation is automatically controlled by the float actuated switch 38.

As stated before, the invention is not limited to a filter which in this instance is back of a chemical plant, since it may be placed back of any other type of plant, or may be the sole unit of a system. In any use that may be made of my trickling filter, the recirculation of the filtered liquid will actively aid the process of oxidation of the polluted liquids, and permit economies of construction and operation that are not possible with filters of the original types.

Having described my invention, I claim:

1. In an apparatus of the type described, a dosage tank to receive polluted liquids, a trickling filter, means to receive the filtered liquid, a single conduit for delivering liquid from said dosage tank to the trickling filter and piping for returning the filtered liquid from the filtered liquid receiving means to said conduit for passage therethrough to said dosage tank for recirculation through the filter.

2. In an apparatus of the type described, means for the chemical treatment and sedimentation of polluted liquids, a dosage tank, means for conducting the liquid from which materials have been removed by chemical treatment and sedimentation, to the dosage tank, a, trickling filter, means to receive the filtered liquid, a single pipe for discharging said treated liquid from the dosage tank to the filter and pining for returning the filtered liquid from the filtered liquid receiving means to said single pipe for passage therethrough to the dosage tank.

3. In an apparatus of the type described, a receptacle to receive polluted liquids, a trickling filter, means for conducting said liquids to the filter, a humus tank, a tank intermediate the trickling filter and humus tank, a discharge line leading from the filter to the intermediate tank, a second line leading from the latter to the humus tank, a return line between the intermediate tank and the first receptacle, a pipe connected between the humus tank and the return line, and pump means for returning the filtered liquid in the intermediate tank, with some solids from the humus tank, to the receiving receptacle.

4. In an apparatus of the type described, a receptacle to receive polluted liquids, a trickling filter, a pipe for conducting said liquids from the receptacle to the top of said filter, means between the bottom of the filter and said pipe to return the filtered liquid to the receiving receptacle, a pump in said line to effect this return, an electric motor for operating the pump, a check valve in said line between the receiving receptacle and the pump, an electric switch, an electric circuit including said motor and switch, and a fioat in said receiving receptacle for actuating said switch, to close the cricuit and start the pump when the liquid descends to a predetermined mint in the receptacle, and to open the circuit and stop the pump when the liquid ascends to a predetermined point in the receptacle.

5. In an apparatus of the type described, a primary settling tank to receive polluted liquids, a trickling filter, an infiuent conduit for distributing liquid over the top of the trickling filter from said tank, a final settling tank, means for conveying the eiliuent from the bottom of said timesasdesiredis carried on inthepreaent intrickling filter to said final settling tank, and.

means for diverting from the flow of said final settling tank a portion thereof and returning the same prior to settling to said conduit to be redistributed over the top of the filter for recirculation therethrough.

6. Apparatus for sewage purification comprising a raw sewage settling tank, a trickling filter, a distributor for distributing sewage uniformly over the top of said trickling filter, a final settling tank, means for conveying filtered sewage from the bottom of said filter to said final settling tank, and means for delivering a mixture of settled raw sewage and freshly filtered sewage to said distributor comprising a conduit from said raw sewage settling tank and a conduit from said conveying means between said filter and said final settling tank, said conduits unit-- ing in a common conduit leading to said distributor.

'7. The apparatus oi claim 6 comprising also means for controlling the delivery of freshly filtered sewage to said comomn conduit so that the amount thereof is greater when the flow of settled raw sewage is lesser and vice versa.

8. A sewage treating process comprising the steps of first flowing raw sewage through a primary settling zone, then passing all of the settled sewage through a biological contact zone by .trickling said sewage downwardly filmwise over aerobic biological slime adhering to filter bed material while exposed to free air, then discharging part oi the flowing ei'iluent from the said biological contact zone to a final quiescent settling zone, diverting part of said flowing eiiluent and delivering said diverted part back into said process at a point intermediate said primary settling zone and said biological contact zone.

9. The process of claim 8 wherein the rate of return of diverted emuent is controlled to aiiord a substantially constant rate of fluid delivery to the biological contact step.

10. In a sewage treating process comprising the steps oi first flowing all the liquid through a primary settling zone, then trickling all the liquid downward through a biological contact zone, then fiowing liquid from the biological contact zone to a subsequent quiescent settling zone and then to waste, the improvement which comprises diverting liquid from sald flow from said biological contact zone in advance of said subsequent settling zone and returning the thus withdrawn liquid with the solids contained therein to the said biological contact zone, and controlling the delivery of such withdrawn liquid so that the amount thereof is greater when the flow from the primary settling zone is lesser and vise versa.

CHARLES H. SHOCK.

CERTIFICATE OF CORRECTIOX. Reissue Ho. 22,141414. February 22, 191A.

CHARLES H. SHOCK.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1;, first column, line 1, claim 5, for the word "of" after flow read --to--; and second column, line 5, claim 8, after "zone' and before the comma insert -and, in advance of said final quiescent settling zone; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the one in the Patent Office.

Signed and sealed this 9th day of May, A. D. 191th.

Leslie Frazer (Seal) Acting Commissioner of Pstents. 

